Preparation of lactone polyesters



I and PREPARATION OF LACTONE POLYESTERS Donald M. Young, New York, N. Y., and Fritz Hostettler, Charleston, and Robert W. McLaughlin, Belle, W. Va., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Application April 13, 1956 Serial No. 577,954

Claims. (Cl. 260-783) This invention relates to an improved processt for polymerizing lactones to form polyesters that are useful as plasticizers and as intermediates inthe preparation of polyurethane resins.

The facility with which the various lactones react and polymerize upon reaction with an organic compound having at least one hydroxyl or amino radical, such a compound being referred to herein as a monoor polyfunctional initiator, to form polyesters having terminal hydroxyl groups has been found to vary considerably. Thus, for example, dimethyl and epsilon-methyl substituted epsilon-caprolactones are difficult to react and polymerize, even with the use of strongly basic ester exchange catalysts, without causing the product to be discolored.

We have made the surprising discovery that the polymerization of lactones generally can be accelerated very much more, without incurring discoloration of the resulting polyesters, than had hitherto been thought possible and that such improvement in the polymerization of lactones applies specifically also to such difliculty polymerizable lactones as epsilon-methyl-caprolactone and the various dimethyl-epsilon-caprolactones. In accordance with the invention, this improvement in the polymerization of lactones is brought about by carrying out the reaction in the presence of a catalytic amount of a metal chelate or a metal acylate of a fatty acid.

The chelates that 'are desirable as catalysts in the method of the invention because of their ability to promote the formation of the polyesters in a very short reaction time are the chelates of such metals as titanium, zirconium, beryllium, magnesium, calcium, strontium, barium, manganese, iron, cobalt, nickel, copper, zinc,

cadmium, mercury, germanium, tin and lead. Among these, the chelates of the metals of group IV-B of the periodic table i. e., the sub-group of the periodic table whose member of lowest atomic number is titanium,

e. g., of titanium and zirconium, are particularly desirable as catalysts because of their ability to produce virtually colorless polyesters in an extremely short reaction time.

The chelates that are particularly attractive as catalysts in the method of the invention are generally the glycol chelates and alkanolamine chelates having, respectively,

the general formulae:

P ted M "ice . 2 in which the Xs are alkyl, aryl, alkaryl or aralkyl radicals, the As and As stand for hydrocarbon residues of glycols and alkanolamines, respectively, the Ms stand for tetravalent metals of group lV-B, the ns are small numbers including one, the Zs are alkyl or allcylol radicals, and the arrows represent dative or secondary bonds.

Glycol chelates of the Formula I include, by way of example, glycol titanates which are usually prepared by interaction of a chelating compound such as a 2,3-diorgano1,3-diol of the general formula:

in which the Xs represent the same or different. alkyl, aryl, aralkyl and alkaryl radicals with an ortho. ester of titanium. Some of the 2,3-diorgano-1,3-diols suitable as chelating compounds are the various hexylene glycols, various octylene glycols, like 2 -ethylhexanediol1,3, various dodecylene glycols, 2,4-diphenylbutanediol-1,3, 2,4- dimesitylbutanediol-1,3, and similar glycols or mixtures thereof. Thus, for instance, the chelate prepared by interaction of 2-ethyl-hexanediol-1,3 with an ortho ester of titanium'is believed to be an dctylene glycol titauate having the formula:

CsH1 02H:

CH- lib-CH1 XO/Tl-0X 0 0K (EHr-CH-JJH 02H! CaHI Alkanolamine chelates of the Formula 11 include, by way of example, alkanolamine titanates which are usually prepared by interaction of an alkanolamine chelating compound, e. g., triethanolamine, N-methyl diethanolamine, N-dimethyl ethanolamine, and like compounds or mixtures thereof. Thus, for instance, the chelate prepared by interaction of triethanolamine with an. ortho ester of titanium is believed to be a triethanolamine titanate having the formula:

In the above chelate formulae, two mols of chelating compound (glycol or alkanolamine) are indicated and they represent the stochiometric quantities necessary to satisfy the maximum coordination numbers ofmetals of group lV-B. However, it is possible to add more than two mols of chelating compound per metal molecule, the additional mols merely replacing one or both OX groups. The glycol and alkanolamine chelates are not distinct compound since they do not form cyclic structures exclusively, but to a limited extent appear to be bridged between the metal atoms to give some degree of polymerization as indicated in the general formulae.

The glycol chelates are insoluble in water and some or all of the OX groups may be hydrolyzed to form the so-called washed chelates. Alkanolamine chelates are soluble in water but will hydrolyze and become unstable on standing. If their aqueous solutions are neutralized,

they become stable. Even if only enough acid to react butyric, heptanoic, lauric, stearic, oleic or linoleic acids can be used to form the corresponding N-salts.

Another group of chelates of the group IV-B metals that isv suitable as catalysts in the method of the invention includes those obtainable by interaction of tetravalent metal acid halides or esters with aldehydes, keto alcohols or dicarbonyl compounds such as diacetone alcohol, betaketobutanol, beta-hydroxybutyraldehyde, aceto acetic acid, diacetyl, acetyl acetone,- andlike compounds or mixtures thereof as described in U. S. Patent 2,680,108 to Schmidt. This group of chelates is again slightly polymeric in nature.

Still another group of chleates of the group IV;-B metals that is suitable includes metal lactates having the general formula:

a=s a at no ngon 6 on B L-(31. on and the salts thereof; 'litanium lactate, for example, forms very stable aqueous solutions which are acidic and may be neutralized without precipitation by cautious addition of alkali. I

The titanium chelatesthat deserve special mention by reason of their outstanding efficacy as catalysts are octylene 2-ethylhexanediol-l,3titanate, hydrolyzed 2-ethy1- hexanediol-1,3 titanate,-- triethanolamine titanate, the stearic acid salts of triethanolamine titanate, the oleic acid salts of triethanolamine titanate, and the linseed acid salts of triethanolamine titanate. Chelates such as manganese ethyl acetoacetate, calcium ethyl acetoacetate and manganese-2,411entanedione, while somewhat less effective, are operable. H t The acylatesfound suitable as catalysts inthe method of theiinvention are generally those believed to have the general formula:

o bake it) --MO- X in which the X's are alkyl, aryl, alkaryl or aralkyl, Ac is a hydrocarbon residue of the monocarboxylic acids such as acetic, butyric, maleic, stearic, lauric, linoleic acid or mixtures thereof, and M is a tetravalent metal of group IV-B. Whereas in the above formula the ratio of monocarboxylicacid to metal is 1: 1 departures from this ratio to f or example; 3:1 are all Within the scope of operable lys v I The titaniumacyla'tes'are" normally prepared by interactionof tetrav'alent titanium esters or halides with a monocarboxylic acid and,if desired, they may be hydi'olj'lzed to replace theJOX' groups by hydroxy]; ,The highsolubility or such" abylates in hydrocarbons and the fact that the solutions: formed" therewith] are non visc'ous indicates that x, representing the degree of polymerization, is a low number. The a'cylate's that deserve particular nientionby reason of their outstanding"effectiveness as catalystsare" the fouowingtitanium acylates: hydroxy titaniumsteai'ate, isoproporty titanium 'stea'rate, hydroxy titanium oleate', isopro'p'oxy titanium oleate, hydroxy titanium soy a'e'ylat'es-g" i'sopropbxy' titanium soy acylates, hydroxy titanium unseen 'acylate's; isopropoxy linseed urn acylate's, hydroxy titanium castor acylates, isopropoxy ti anium casto'r acylates, hydroxy titanium tall 'i1se 1"s-,iso epoxy itaniuintall oilacylates,'hydroity titaniuiii'coeo t acyl a t es and isopropoiry titanium coconut acylate s.

While the method of the inventionis particularly usefill in the polymerization of lactones that are difiicult and perhaps even impossible to polymerize by other means, it is also of considerable advantage in the polymerization of other lactones that are not difiicult to polymerize. The method has theunique distinction of not only reducing reaction time very substantially, i. ,e,,.from a matter of days and even weeks to a 'few hours, but also of minimizing and in most instances avoiding discoloi d tion of the end product. I a

The lactone used as a starting material may beany lactone, or combination of lactones, preferably having six or more carbon atoms in thering, Lactones having five or less carbon atomscinnthe. ring are considered un suitable for the purposes of the invention because of the tendency that polymers thereof have to revert to the monomer at elevated temperature. One or more of the carbon atoms in the lactone ring may be substituted by alkyl, cycloalkyl, alkoxy or aromatic radicalscontaining up to about twelve carbon atoms. The lactones preferred as starting materials in the method of the invention are those having the general formula:

wherein a is at least foulgat least n+2 Rs are hydrogen, the remainder of the Rs are hydrogen, alkyl, cycloalky l, alkoxy or single ring aromatic hydrocarbon radicals, none of the substituents contain more than about twelve carbon atoms, and the total number of carbon atoms" the substituents on a lactone ring does not exceed about twelve. Lactones having greater numbers of substituents other than hydrogen on the ring are considered unsuitable for the purposes of the invention because of the tendency that polymers thereof have to revert to the monomer; particularly at elevated temperature. Unsuhstituted epsiloncaprolactone, in which n. is four and all the Rs are hydrogen, is derived from 6-hydroxyheiranoic acid. Substituted epsilon-caprolactones, and'rnixtures thereof, are available by reacting a corresponding substituted cyclohexanone with an oxidizing agent such as peracetic acid, as described in copending application Serial No. 548,754, filed November 23, 1955. The cyclohexanones may be obtained from substituted phenols or by other convenient synthetic routes. 7

Among the substituted epsilon -caprolactones considered most suitable as starting materials in the method of the invention are the various monoalkyl epsilon-eaprolaetones su'ch as the monomethyl-, m'ono'ethyh', monopropyl monoisopropyh, etc. to monododecyl epsilon-caprolao tones; dialk'yl epsilon-caprolact'ones in which the two aikyl groups are substituted on the same or different carbon atoms, but not both on the epsilon carbon atoms; trialkyl epsilon-caprolactones in which two or three carbon atoms in the lactone ring are substituted, so long as the epsilon carbon atom is not disubstituted; alkoxy epsilon-captolactones such as methoxy and ethoxy epsilon-caprolactones; and cycloalkyl, aryl, and aralkyl epsilon-caprolacto'ne's such as cyclohexyl, phenyl and benzyl epsiloncaprolactones. Mixtures of substituted lactones and mixtures of substituted lactones with unsubstituted lactones have been found to be particularly desirable.

Lactones having more than six carbon atoms in the ring, e. g., zeta-'enantholactone and eta-caprylolactone, may also be polymerized in accordance with the method of this invention. I A

The initiators that are preferred in the method of the invention are represented by the general formula heterocyclic radicals, y is a number equal to the functionality of the initiator," and the Ys stand for -O-.

--NH and NR"-, R" being alkyl, and, aralkyl or cycloalkyl. These include monofunctional initiators such as alcohols and amines, that have a reactive site capable of opening the lactone ring and adding it onto the initiator as an open chain without forming water of condensation, and polyfunctional initiators such as polyols, polyamines, amino alcohols, and vinyl polymers, as well as amides, sulfonamides, hydrazones, semicarbazones and 'oxirnes having two or more such reactive sites.

Alcohols that are useful as monofunctional initiators include primary, secondary, and tertiary aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, lbutanol, Z-butanol, tert.-butanol, l-pentanol, 3-pen'tanol, tert.-amyl alcohol, l-hexanol, 4-methyl-3-pentanol, 2- ethyl-l-butanol, 1-heptanol, S-heptanol, l-octanol, 2- ethyl-l-hexanol, l-nonanol, 2,6-dimethyl-4-heptanol, 2,6,8-trimethyl-4-nonanol, S-ethyI-Z-nonanol, 7-ethyl-2- methyl-4-undecanol, 3,9-triethyl-6-decanol, and lauryl alcohol; aromatic alcohols such as benzyl alcohol and phenyl'methyl carbinol; and cycloaliphatic alcohols such as cyclohexanol and trimethylcyclohexanol.

Amines that are useful as monofunctional initiators include primary and secondary aliphatic amines such as methyl, ethyl, n-propyl, isopropyl, n-btuyl, scc.-butyl, isobutyl, tert.-butyl, n-amyl, n-hexyl and Z-ethylhexylamine, as well as the corresponding dialkyl amines; aromatic amines such as aniline, ortho-toluidine, meta- -toluidine, para-toluidinc, and diphenylamine; cycloaliphatic amines such as cyclohexyland dicyclohexylamine; and heterocyclic amines such as pyrrolidine, piperidine, and morpholine.

Diols that are suitable as bifunctional initiators include glycols of the formula HO(CH ),,0H in which n equals 2 to 10, glycols of the formulae HO(CH CH O),,H and HO(CHCH CH O),,H in which n equals 1 to 40, 2,2- dimethyl-l,3-propanediol, 2,2-diethyl-l,3-pr0panediol, 3- methyl-1,5-pentanediol, N-methyland N-ethyl diethanolamines, various cyclohexanediols,

4,4-methylenebiscyclohexanol, a

various hydroxyrnethyl-phenethyl alcohols,

C H: Q H2 0 H -various hydroxymethyl-phenylpropanols,

C H: 0 H

CHsCHsOHaOH various phenylenediethanols,

CH|CH|OH C HaGHgOH various phenylenedipropanols,

0 H2 C H: C H: 0 H

CHIGHjCHzOH HO-CHzCHzN' Other suitable diols include polyoxyalkylated derivatives of difunctional compounds having two reactive hydrogen atoms. These difunctional compounds may contain primary or secondary hydroxyls, phenolic hydroxyls, primary or secondary amino groups, amido, hydrazino, guanido, ureido, mercapto, sulfino, sulfonamido, orcarboxyl groups. They are obtainable by reacting diols or theclass HO (CH ),,OH, where n equals 2 to 10, propylene glycol, thiodiethanol, xylenediols, 4,4'-methylenediphenol, 4,4-isopropylidenediphenol, and resorcinol; mercapto alcohols, like mercaptoethanol; dibasic acids, such as maleic, succinic, glutaric, adipic, pimelic, sebacic, phthalic, tetrahydrophthalic, and hexahydrophthalic; phosphorous acid; aliphatic, aromatic, and cycloaliphatic primary monoamines, like methylamine, ethylamine, propylamine, butylamine, aniline, cyclohexylamine; secondary diamines, like N,N-dimethylethylenediamine; and amino alcohols containing a secondary amino group, like N-methylethanolarnine, with alkylene oxides such as ethylene oxide, propylene oxide, l-butylene oxide, 2- butylene oxide, isobutylene oxide, butadiene monoxide, styrene oxide, and also mixtures of these monoepoxides.

The preparation of the polyoxyalkylated derivatives is illustrated by the reaction of 1,4-butanediol with ethylene oxide:

H(O CHaCHa) s0 (CHriaO (CHBCHIO)|H where a=b+c=1 to 40.

Further useful bifunctional initiators are polymers of monoepoxides obtainable by polymerizing with such catalysts as oxonium salts of hydrogen halides;-metal or nonmetal halides whose etherates are oxonium complexes; electrophilic metal or non-metal halides in the presence of hydrogen halides, acyl halides, or anhydrides of inorganic and organic acids; and inorganic acids or anhydrides thereof whose anions show little tendency to polarize. Polymers containing hydroxyl end-groups may be obtained by treating these products with alkaline reagents upon completion of the polymerization reaction. Among suitable monoepoxides for preparing such polymers are tetrahydrofuran, trimethylene oxide, propylene oxid ethylene oxide, or mixtures thereof.

Higher functional alcohols suitable for initiating the polymerization of lactones include triols such as glycerol, trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, N-triethanolamine, and N-triisopropanolamine; various tetrols like erythritol, pentaerythritol, N,N,N',N'-tetrakis- (Z-hydroxyethyl)ethylenediamine,

cmcniorr OHaOHaOH 7 and N,N,N',N' tetrakis(2 hydroxypropyl)ethylenediamine;

CH: CH: HOCIHICHQ CH: HOH

CHQCHZN HocHd 2 CHzGHOH (H: lHa

pentols, hexols, like dipentaerythritol and sorbitol; alkyi glycosides; and carbohydrates such as glucose, sucrose, starch, and cellulose.

Also suitable as polyols are the polyoxyalkylated dc rivatives of polyfunctional compounds having three or in'ore -'reactive-hydrogen atoms as,-for example, the re action product of trimethylolpropane with ethylene oxide in accordance with the reaction:

w ere a -fb+'c+u='s 45. H

I niad'dition to the polyoxylak'ylated derivatives of t'riiiietliylolpropane, those of the following compounds are "likewise suitable: glycerol, 1,2,4-butanetriol, 1,2 6-hex- -:uietriol, 'erythritol, pentaerythritol, sorbitol, methyl gly- "fcdsides,"gluco s'e, sucrose, diamines of the general formula H N CH ,',NH where n equals 2 to 1'0, 2'-('methyl ai'nirio) eth'ylamine, various phe'nyleneand toluene-diainines, benzidine, 3,3'-dimethyl 4,4'-biphenyldiamine,4;4'- methylenedianiline, 4,4',4"-methylidynetrianiline, cycloaliphatic diamines, like 2,4-cyclohexanediamineand 1- "iriethyl z,4-cyclohexanediamine, amino alcohols ofthe ge era1 formula HO(CH ),,NI-I where n equals 2'to l0, 'dietliylen'etriamine, triethylenetetramine, 'tetraethylene- "pentaniine, poly-carboxylic acids like citric acid, aconitic acid,

110 o o-cH=c-orn-c 0 OH mellitic acid,

* difpolyfunctional inorganic" acids like phosphoric acid. Difunctionala'mino" alcohols capable of initiating the "'polymefizationof laetones include aliphatic amindlc'ohols of the generalformula-HO(CH ),,NH wheren' equals '2' to 10, N methylethanolamine I 'C H3 H0 onto HzNH isopropanolamine,

1 CH: H0 (J HCHzN-H:

has

5-8 N-methylisopropanolamine,

CH: CH: 'HOAHCH:H aromatic amino alcohols like para-'amino-phenethyl *alcohol,

CHQC'HQOH N H: and; para-aminmalpha-methylbenzyl alcohol,

CHOHCHa v:atm-l various eycloaliphatic amino alcohols cyclohexanol.

I NH:

Higher "functional amino alcohols having a total of 'at 'leastthreehydroxy and primary or secondary amino groupsthat are suitable include"diethanolamine,-diisopropanolamine, 2-(2-aminoethylamino)ethanol,

2-amino-2 (hydroxymethyl) 1 ,3-propanediol,

Boom-(Portion OHzOH and 2-amino-2-methyl-1,3-propanediol.

H0 GHQ-041E101;

Suitable diamines include aliphatic diamines *of-iuthe general formula "H N(CH ),,NH monosecondary diamines of the "general formula"RNH(CH;-,),,NH=, and disecondary diaminesof the general formula Higher functional polyamines typical of those suitable for use in the method are: diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diisopropylenetrb amine, triisopropylenetetramine, =tetraisopropylenepent- 9' amine, 1,2,5 benzenetriamine, toluene 2,4,6 triamine, 4,4347'-methylidynetrianiline,

and polyamines obtained by intereaction of aromatic monoamines; with formaldehyde or other aldehydes, for example:

N H; NH:

H: e l

7 Other vinyl polymers that are suitable include polyvinyl alcohol, copolymers obtainable by copolymerization of a mers containing primary or secondary hydroxyl or amino groups or other groups containing reactive hydrogen atoms. Among the vinyl monomers from which such copolymers may, for example, be obtained are: ortho-,, meta-, or para-aminostyrene,

NHz 3-butene-1,2-diol CH =CH-CHOH-CH OH, allyli alcohol, methallyl alcohol, 3-phenyl-3-butene-1-ol,

GHHCHgOH rings and thereby of adding more and more lactone to the molecule. Thus, for example, the polymerization of epsilon-caprolactone initiated with a monoamine is believed to proceed primarily as follows:

ll R'NH; CHgCHaCHzOHzCHgC=O I RNHO (GHOtOH A polyfunctional initiator is believed to open the lactone ring in a similar manner but to produce an ester having several terminal hydroxyl groups that are capable of opening further lactone rings and thereby of adding more and more lactone to the molecule. Thus, for example, the polymerization of epsilon-caprolactone initiated with a diol is believed to take place primarily as follows:

0 l HOB/OH CHzCHzCHgCHaCHzC=O HOROJHCHmOH wherein a is the total number of mols of lactone reacted per mol of initiator and b+c=a.

It will be apparent from these equations that the number of lactone residues in the final polyester will depend in large part upon the molar ratio of lactone to initiator.

The polymerization is, in accordance with the invention, carried out by heating a lactone, or combination of lactones, with an initiator in the presence of the catalyst. Generally, the catalyst should be present in a catalytically significant amount, i. e., between. about 0.001 and about 1% by weight, based on the amount of lactone in the reaction mixture. The preferred range of concentration for the catalyst is between about 0.01 and about 0.2%, this more limited range being preferred because of the uniformly excellent results that are obtained. Very small concentrations below the preferred vinyl monomer Such as ethylene with other vinyl mono mmnnum of 0.01% are, however, efiectlve in providing fairly satisfactory polymerization rates. Amounts in excess of the maximum preferred amount of 0.2% shorten reaction time and are not harmful, although amounts in excess of about 1% should be avoided in order to avoid discoloration of the polyester.

The temperatures to which the reactants are heated may vary from about 50 to about 300 C. Temperatures above this range are to be avoided because of the instability of the reactants and the products at such higher temperatures, whereas reaction temperatures below about 50 C. will result in prolonged reaction time. Temperatures within the range of about 200 C. are preferred because discoloration of the products is thereby avoided while a desirably rapid rate of reaction is retained.

The time of heating depends upon the particular combination of lactone and initiator, as well as upon the particular catalyst employed and its concentration. It is readily ascertainable for any given starting materials,

catalyst, catalyst concentration and temperature conditions by following the progress of the polymerization.

with refractive index measurements. The reaction may be regarded as complete as soon as the refractive index becomes constant. Generally, the reaction time will vary from a few minutes to not more than forty-eight hoursand more usually between about one and twenty-four" hours.

It is preferable, in order to obtain a product of lightco r. to duc he r ian, i h abs o e i en- This may be accomplished, for example, by operating in a partialvacuum min the presence of an inert gas such as nitrogen, which may be passed through the reaction mixture. After the polymerization is completed, any unreacted monomer may be removed by applying a vacuum thereto at elevated temperature, e. g., a vacuum of 1 to 5 mm. mercury at 120 to 160 C.

The proportion of lactone to initiator may vary widely depending upon the particular properties desired in the polyester or the products to be made therefrom. Where the polyester is to have substantially the properties of a product having a succession of lactone residues, the proportion of initiator to lactone may be very small, inasmuch as theoretically one molecule, of initiator is sutficientto initiate the polymerization of an infinite, number at l c e e m ul s. On t e o e an h re a p ytlms na ini s used and it s es red th h p yest nrq ue b of a con g ted str st r n whi h the random distribution of lactone residues and polyfunctional compound residues is more or less alternating or Where the polyfunctional initiator is a high molecular weightmaterial such, as polyethylene glycol or vinyl polymer, the relative proportions may be approximately equal.

The polyester polymerization products obtained in accordance with the invention have molecular weights generally within the range of about 500 to about 12,000, hydroxyl numbers between about and about 350, caroxyl numb s up t bou 7 and preferably e o 5 and at least one active terminal group, usually hydroxyl, the number of active terminal groups depending upon the tunetiona i y f th init to The polyesters are suitable for reaction with ieocyates a ar po yur tha es of; high m lecular wei an superior properties that may be foamed or unfoamed, elastomeric orrigid, as desired. The elastomeric prodnets are outstanding particularly as, tov flexibility at low temperatures and ability to be stored for; indefinite periods of time without prematurehardening, In addit n, the polyesters of the inventionare eminentlysuitable' as plasticizers in various resins, e. g., vinyl chloride-vinyl acetate resins, particularly if they are acylated in known manner to insolubilize the terminal hydroxyl groups and thus improve their resistance to extraction by water from resins with which they are combined.

As plasticizers, the polylactones of the invention have the unique advantage, hitherto. so elusive in the development of plasticizers, of combining excellent low temperature performance, i. e., imparting good flexibility to resins even at temperatures below zero, with low volatility and high resistance to water and oil extraction. They are available as easily-pourable liquids, and are therefore susceptible to facile handling and mixing as compared with the highly viscous, non-pourable plasticiiers'here tofore available. At the same time, the plasticizers-'of the invention are non-toxic and light-stable.

The utility and advantages derived from the useof the catalysts in accordance with the invention will become further apparent from the following examples included to illustrate the best modes now contemplated for carrying out the invention.

Several representative substituted epsiloncaprolactoucs were polymerized by heating to various temperatures with an amount of ethylene glycol calculated to yield an average molecular weight of 2200 without a catalyst and with representative concentrations of the catalysts indicated in the table below. The; catalyst concentrations are in terms of percent by weight of lactone and the procedure in each polymerization was. to add; the catalysts; after the reactants had reached the indicated temperatures The; progress of the polymerization was followed; and polymerization time was determined, by, means of? the refractive index, which becomes; constant; when R011. merization is complete.

Catalyst Temper,- Epsilon-Caprolactone Catalyst Ooncenature, Time.

tration, O. hm Percent Mixed Alphaand epsllon- None. 170 102 methyl.

D o... Octylene glycol 0.1 170 1,75

titanate. Do 0.05 170. 1,5,.(0). D,o.. do-.- 0. 1 7. 25' Do. -.do.. 0.06: 9.115% 130.. ..do.. 01, 130, Do.. do 0.05 130' D o.. Trlethanolamtne. 0:051 I 212MB);

tltanate. Do Trlethanolamine 0:05 170 3.2509- titanate-N-oleate. Do Hydroxytltanium 0.1, 170 l 4.01);- oleate. Do Hydroxytltanlum 0.1 170 4(0) stearate. Do Isopropoxytitanium 0.1 170 1.86)

oleate. Do. Isopropoxytitanlum 0.1 170 1.6(3)

stearate. L10 Manganese ethyl 0.1 170 11.25

acetoacetate. 10o Manganese 2,4- 0.1 170 17 pentanedione. Do 'Galcium ethyl 0.1 170; 'acetoacetate, Beta, delta-dimethy None.. 170' I 108.- Do Octylene glycol 0. 1 110 5 tltanate. Isopropoxytitanlum 0. 1 170 0. 1

stearate. ---.do 0.5 170 0.18 .do 0.01 170 0.66 ....do. 0.1 160 0.5 005 160 1.0 do. 0.01 150 1.13 do- 0. 1 130 1. 09 --...-do 0.05 130 i 1.66 0 .do. 0.01 r 130 6:3 Mixed beta,- and delta methyL- None 170 29: Do Octylcne glycol 0.05 170 1.26-

tltanate. 3 1 I00 Isopropoxytltanlurn 0.1 170 0 2; stearate. r

Hydroxyl Oarhoxyl Molecular Example Number Number Weight (calculated) It is apparent that various modifications will readily occur to those skilled in the art upon reading this description. All such modifications are intended to be included within the scope of the invention as defined in the accompanying claims.

We claim:

1. In a method of preparing a polyester by heating a lactone having from six to eight carbon atoms in the ring with an organic compound having at least one reactive radical capable of opening the lactone ring, said radical being a member selected from the group consisting of hydroxyl and amino radicals, said organic compound being reactive with the lactone only by virtue of said radicals, the improvement which comprises carrying out the reaction in the presence of a catalytic quantity of a catalyst selected from the group consisting of chelates and fatty acid acylates of a metal in group IV-B, said group IV-B being that sub-group of the periodic table whose member of lowest atomic number is titanium.

2. In a method of preparing a polyester by heating a lactone having six carbon atoms in the ring with an organic compound having at least one reactive radical capable of opening the lactone ring, said radical being a member selected from the group consisting of hydroxyl and amino radicals, said organic compound being reactive with the lactone only by virtue of said radicals, the improvement which comprises carrying out the reaction in the presence of a catalytic quantity of a titanium chelate.

3. In a method of preparing a polyester by heating a lactone having six carbon atoms in the ring with an organic compound having at least one reactive radical capable of opening the lactone ring, said radical being a member selected from the group consisting of hydroxyl and amino radicals, said organic compound being reactive with the lactone only by virtue of said radicals, the improvement which comprises carrying out the reaction in the presence of a catalytic quantity of a titanium chelate selected from the group consisting of 2-ethylheXanediol-1,3-titanate, triethanolamine titanate and the N-salts of triethanolamine titanate.

4. In a method of preparing a polyester by heating a lactone having six carbon atoms in the ring with an organic compound having at least one reactive radical capable of opening the lactone ring, said radical being a member selected from the group consisting of hydroxyl and amino radicals, said organic compound being reactive with the lactone only by virtue of said radicals, the improvement which comprises carrying out the reaction in the presence of a catalytic quantity of a fatty acid acylate of titanium.

5. In a method of preparing a polyester by heating a lactone having six carbon atoms in the ring with an organic compound having at least one reactive radical capable of opening the lactone ring, said radical being a member selected from the group consisting of hydroxyl and amino radicals, said organic compound being reactive with the lactone only by virtue of said radicals, the improvement which comprises carrying out the reaction in the presence of a catalytic quantity of a fatty acid acylate of titanium selected from the group consisting of hydroxyand isopropoxy-titanium stearates, -oleates, -soy acylates, -linseed acylates, -castor acylates, -tall oil acylates and -coconut acylates.

References Cited in the file of this patent UNITED STATES PATENTS 2,153,801 Hovey et a1. Apr. 11, 1939 2,361,036 Hung Oct. 24, 1944 2,455,731 Caldwell Dec. 7, 1948 2,555,385 Watson June 5, 1951 2,621,193 Langkammerer Dec. 9, 1952 OTHER REFERENCES Parkington: A T ext-Book of Inorganic Chem., 6th ed., 1953, Macmillan & Co.; inside back fiyleaf, Short Periodic Table.

Chem. and Eng. News, vol. 33, October 1955, pp. 4226-4228. 

1. IN A METHOD OF PREPARING A POLYESTER BY HEATING A LACTONE HAVING FROM SIX TO EIGHT CARBON ATOMS IN THE RING WITH AN ORGANIC COMPOUND HAVING AT LEAST ONE REACTIVE RACICAL CAPABLE OF OPENING THE LACTONE RING, SAID RADICAL BEING A MEMBER SELECTED FROM THE GROUP CONSISTING OF HYDROXYL AND AMINO RADICALS, SAID ORGANIC COMPOUND BEING REACTIVE WITH THE LACTONE ONLY BY VIRTUE OF SAID RADICALS, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT THE REACTION IN THE PRESENCE OF A CATALYTIC QUANTITY OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF CHELATES AND FATTY ACID ACYLATES OF A METAL IN GROUP IV-B, SAID GROUP IV-B BEING THAT SUB-GROUP OF THE PERIODIC TABLE WHOSE MEMBER OF LOWEST ATOMIC NUMBER IS TITANIUM. 